Heterotopic ossification (HO), the formation of ectopic bone in skeletal muscle and other connective tissues, is an important cause of morbidity from joint immobility and pain. Fibrodysplasia ossificans progressiva (FOP), a rare form of HO, is inherited as an autosomal dominant trait and is typically associated with activating mutations in Acvr1, the gene encoding the BMP type I receptor, ALK2. Individuals with FOP only have minimal skeletal abnormalities at birth, but extensive HO affecting nearly all skeletal muscles, ligaments and fascia is triggered after birth by traumatic injury or inflammation. No effective treatments currently exist for FOP patients, and disease progression results in severe restriction of joint function and premature mortality. In 2008, the principal collaborators identified the first small molecule inhibitor of BMP signaling. The compound, dorsomorphin, blocks BMP signaling by inhibiting BMP type I receptors. Dorsomorphin derivatives were developed through initial medicinal chemistry optimization. The overall objective of this research is to advance the development of a dorsomorphin derivative in preparation for clinical testing in patients with FOP. The research team will use the resources and expertise of the TRND program to complete scaled-up synthesis; development of an optimal oral formulation; studies of pharmacokinetics, absorption, distribution, metabolism, excretion and toxicology; product development planning and preparation for submission of an Investigational New Drug (IND) Application with the FDA; and, possibly, Phase I tolerability studies. TRND researchers determined that the initial lead molecule was unsuitable for further preclinical development. As such, TRND scientists are performing medicinal chemistry optimization to identify a compound suitable for formal preclinical development. Once such a compound is identified, TRND will conduct the necessary studies to support filing an IND Application with the FDA.